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Saving water, saving energy

Posted:
04/08/2014 03:00:00 AM EDT

In this weekly column, I’ve focused a lot of attention on the energy-saving measures at our new home -- from the innovative insulation materials we used to the air-source heat pump heating system and our top-efficiency heat-recovery ventilator. What I haven’t said much about are the measures we’ve taken to reduce water use and why these measures save energy as well.

The water-energy nexus

Before getting into specifics, it’s important to note that there is a close relationship between water and energy -- even when we’re not talking about hot water. At the macro scale, it takes at lot of water to produce energy.

With electricity generation, each kilowatt-hour (kWh) of electricity generated (based on national averages) consumes 2.0 gallons of water, according to a 2003 paper by National Renewable Energy Laboratory researchers. This is mostly from evaporation of water at thermoelectric power plants, but also includes evaporation of water at reservoirs used for hydropower generation.

Other energy sources consume a lot of water in production. We can refer to this as the "embodied water" of these energy sources. Simply pumping oil out of the ground isn’t all that water-intensive, but when we start getting into "enhanced recovery" technologies like hydraulic fracturing (fraking) the water intensity goes way up -- and can be a limiting factor. It may increasingly lead to conflicts with farmers in arid regions that are rich in underground oil and natural gas.

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At the same time, treating and distributing water and treating wastewater use a lot of energy. This is especially the case with municipal water and sewer systems, but even in rural areas with their own water systems, water pumping can be one of the largest energy consumers -- to operate deep-well, 220-volt, submersible pumps.

Water conservation

It is with this context that I consider water conservation to be an extremely important priority. We are fortunate in Vermont to have plenty of water, but I’m just back from California, which is dealing with one of the most severe droughts in decades. Flying over the Sierras on my way there I was shocked to see how little snow cover there was.

So what are the water conservation measures we implemented at our new house?

Low-flow showerheads

We installed EPA WaterSense-certified showerheads that deliver 1.75 gallons per minute (gpm), vs. the federal standard 2.5 gpm for showerheads. Ours are Kohler Bancroft showerheads, and we are very pleased with them, though I’ve also used a Delta H2Okinetic showerhead using just 1.5 gpm and been very happy with that, and I recently used a Niagara Conservation showerhead rated at just 1.0 gpm and found that to work just fine.

When we save water with a showerhead or faucet we also typically save energy use directly, since we’re using less hot water. Indeed, in replacing older, high-flow showerheads with new low-flow models, the payback for that change is often measured in months or even weeks, instead of years.

Low-flow faucets

The Kohler faucets in our two bathrooms are WaterSense-certified at 1.5 gpm, vs. the maximum 2.2 gpm. Interestingly, almost the entire plumbing industry has shifted to 1.5 gpm flow rates -- the level required for WaterSense certification. Because we rarely turn on the faucet full-force, our actual consumption is a lot lower. Screw-in faucet aerators are inexpensive and can quickly convert most standard faucets to water-saving versions.

Low-flush toilets

We have two bathrooms: upstairs and downstairs. Both have Kohler "high-efficiency toilets" that use just 1.28 gallons per flush (gpf). I admit to having been somewhat skeptical that 1.28 gpf would be enough for satisfactory performance, but in the three months we’ve been in the house we’ve had zero problems. The toilets are performing beautifully.

Water-efficient clothes washer

I remember when I bought my first new clothes washer 25 or 30 years ago, I had to work pretty hard to find a water-conserving horizontal-axis (front-loading) model. At the time there was only one U.S. manufacturer producing such a product for home use (White-Westinghouse).

Fortunately, it is a very different situation today, with nearly every manufacturer offering such products. We bought a Whirlpool Duet washer, which I think is the best of the U.S.-made models. We had one in our last home and were very pleased with it. The only difference with this purchase is that the washer (and matching dryer) are larger, since Whirlpool shifted manufacturing to the U.S. from Mexico, and the units grew in size.

Because we typically wash clothes in cold water, our direct energy use for clothes washing is very low.

Water-efficient dishwasher

We bought a KitchenAid, mid-range dishwasher (Model KUDE20FBSS) and are very pleased with it so far. We operate it with the no-heat-dry feature selected on a normal or light cycle to further reduce water and energy use. Roughly 90 percent of the energy use by dishwashers is for heating the water, so a water-conserving dishwasher also saves a lot of energy. With the Normal cycle and assuming typical soiling of dishes, a load of dishes uses just 2.9 gallons -- far less than was the case a decade ago.

It’s worth noting that using a modern, EnergyStar-rated dishwasher typically uses a lot less water than washing dishes by hand.

Knee-control kitchen faucet

We brought down from the house we moved out of a great kitchen faucet control system made by TapMaster that lets you turn the faucet on and off by either pressing your knee into one of the under-sink cabinet doors or by pressing a toe plate with your foot. This way you can easily turn the water on and off while you’re washing a pot or rinsing dishes. There’s no reason to leave the water running, so moderate water savings can be achieved. It’s also a huge convenience!

Final thoughts

In the years and decades ahead, water may well be a bigger challenge than energy in many areas of the U.S. and world. We should all do our part by using this precious resource efficiently.

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